Recently, especially in United States, the needs is rapidly increasing for the lens made of plastic base material using a polycarbonate resin having excellent impact resistance, for the use of the sunglasses with a dizziness prevention property. Further, in regards with such plastic sunglass, the photochromic sunglass made of plastic (photochromic lens) is rapidly becoming popular which can control the dizziness prevention property by changing a transparency depending on the surrounding brightness by comprising a photochromic pigments.
Such photochromic lens is produced by various methods. Specifically, the method of coating a coating composition including the photochromic compound on the surface of the plastic lens, and the method of forming the lens by mixing the photochromic compound to the material of the plastic lens itself or so may be mentioned.
Also, the following method is also being considered from the point of being able to carry out a partial process, being able to form the smooth photochromic layer, and being able to provide the photochromic characteristic simultaneously with the production of the plastic lens by injection molding. That is, it is a method using the photochromic adhesive agent including the photochromic compound and the urethane polymer. Specifically, in said method, “the photochromic laminated article” of which said photochromic adhesive agent is layered on the optical sheet such as polycarbonate resin or so is produced, then said laminated article is inserted in the metal mold for the lens molding, then the injection molding or the thermocompression or so is carried out. According to this method, the photochromic sunglass made of plastic having laminated article can be produced (refer to Patent articles 1 to 4). The photochromic lens obtained by said method (the optical article) binds said laminated article and the plastic lens by the injection molding or the thermocompression; hence the adhesiveness at the boundary of the laminated article and said lens are extremely strong.
However, in the optical article produced by the method asserted in the Patent article 1 and 2, there was a problem that the optical sheet was released since the adhesiveness between the optical sheet and the photochromic adhesive agent was not sufficient, which is thought to be caused by the structure of the used urethane polymer (the adhesiveness of the photochromic laminated article itself is not sufficient, hence the optical sheet was released in some case). Further, since the heat resistance of said urethane polymer is not sufficient; in some case the optical strain or so was generated when carrying out the injection molding or the thermocompression or so. Therefore, it is in need to enhance the heat resistance of the matrix resin (the urethane polymer) of the layer formed by said adhesive agent.
On the other hand, in the method recited in Patent articles 3 and 4, it employs the 2 liquid type urethane polymer (the mixture between the compound having the isocyanate group at the end terminal and the compound having the hydroxyl group at the end terminal). In this method, the composition including the 2 liquid type urethane polymer and the photochromic compound is layered on the optical sheet, and after this layering, the 2 liquid type urethane polymer is reacted to form the urethane resin layer having high molecular weight (the adhesive agent layer). According to this method, since said composition of before layering has relatively low molecular weight, it is advantageous since the solubility of said composition itself and the solubility of the photochromic compound are not lowered. Further, the heat resistance is also enhanced since the 2 liquid type urethane polymer is reacted to form the high molecular weight urethane polymer after layering.
However, even for the photochromic composition obtained by this method, the adhesiveness of the photochromic multilayered body itself was not sufficient, and the releasing of the optical sheet was not resolved. The photochromic sunglass made of plastic is exposed under highly humidified environment, or is in contact with warm water when using in a daily life. Thus, it has to have high adhesiveness between the optical sheet and said adhesive agent even under such condition. That is, even when the photochromic layered body itself is under such condition, it is demanded that the optical sheet is strongly bonded. However, the photochromic adhesive agent obtained by reacting said 2 liquid type urethane polymer was difficult to maintain the high adhesiveness between the optical sheet and said adhesive agent after being in contact with a hot water while maintaining the high photochromic characteristic, thus there was a room for improvement.
Also, the following method is proposed which is a method for producing the lens by using “the photochromic laminated article” and it is a method other than the aforementioned injection molding or thermocompression. Specifically, it is a method of forming the plastic lens in which the photochromic laminated article is immersed into the polymerizable monomer, and said polymerizable monomer is polymerized and cured (the Patent articles 5 and 6). According to this method, by changing the type of the polymerizable monomer, the property of the obtained lens can be easily changed, thus the lens with various properties can be produced. Also, since the photochromic lens can be produced at relatively low temperature compared to the injection molding or the thermocompression, hence this method is excellent in a sense that the strain of the lens caused by the heat can be reduced.
However, according to the examination by the present inventors, by the method recited in the Patent articles 5 and 6, the followings still needed to be improved. In the Patent articles 5 and 6, as the photochromic adhesive agents, it is recited that 2 liquid type thermal curing urethane polymer formed of the urethane polymer having the isocyanate group and a curing agent was used. By using the thermal curing urethane polymer recited in the Patent articles 5 and 6, depending on the type of the polymerizable monomer and the polymerization condition, in some case the thermal curing urethane polymer and the photochromic compound eluted out to the polymerizable monomer from the photochromic laminated article. This elusion occurred at the end portion of the photochromic laminated article. The portion causing the elution of the photochromic laminated article must be removed from the lens, thus the larger the elution portion becomes, the smaller the effective area of the lens becomes. Also, when the elution portion is removed from the lens, the end face of the photochromic laminated article exist on the same face as the end face of the photochromic lens; however in case of the thermo curing urethane polymer, the adhesiveness was not sufficient in some case, and there was a chance of lens being released.
Further, the Patent article 7 discloses the method for producing the photochromic lens wherein, the photochromic urethane polymer having acryloyl group at the side chain is obtained by reacting the isocyanate compound and the diol compound having the acryloyl group under the presence of the photochromic compound, then coating this to the substrate surface. However, in the photochromic urethane polymer used in this method, the amount of said acryloyl group included therein was 210 to 400 mmol in 100 g of the photochromic urethane polymer. Thus, it is thought that due to this, the adhesiveness between the base material and the photochromic urethane polymer coated on the base material surface has insufficient adhesiveness; hence the photochromic urethane polymer was released.    [Patent Article 1] US Patent Publication No. 2004096666    [Patent Article 2] JP Patent Application Laid Open No. 2003-519398    [Patent Article 3] US Patent Publication No. 200502333153    [Patent Article 4] US Patent Publication No. 20020006505    [Patent Article 5] JP Patent Application Laid Open No. 2005-181426    [Patent Article 6] JP Patent Application Laid Open No. 2005-215640    [Patent Article 7] JP patent Application Laid Open No. 2006-513276